Liquid waste management including grease trap pumping, has become a lucrative business. With the growth of the recycling industry, waste grease is now a commodity, and restaurants no longer pay for grease removal services. Rather, recyclers pay for waste grease, and recondition and sell it.
A grease trap pumping operation typically involves a tanker truck with a large hose that is inserted into the grease trap of the restaurant or other establishment. The grease is vacuumed out of the trap and through a metering device that measures the amount of grease that is removed. The removal service pays the establishment based on the total amount of grease that is registered through the meter.
There have been continuing problems in providing an accurate measurement of the total amount of grease that is removed. In particular, there is a period of time in the beginning of the removal operation when the vacuum is first started and at the end when the grease trap becomes empty, that air is pulled through the metering device and is erroneously measured as liquid. This gives a false reading of the total amount of grease that is removed, at a substantial cost to the removal service.
Metering devices directed toward solving this problem have had limited success. Several of these devices include air eliminator mechanisms. For example, U.S. Pat. No. 3,299,704 (Wilson) discloses an apparatus that includes a by-pass to remove gas from the system and prevent liquid flow through the meter when gas accumulates to a certain level. U.S. Pat. No. 3,404,567 (Berck) discloses an apparatus for channeling air through a by-pass line around the fluid meter. U.S. Pat. No. 4,949,577 (Schnitzler) discloses a metering assembly that includes an air eliminator vessel where air is eliminated through a vent tube.
Other devices are constructed to interrupt the flow of fluid through the meter. One such device, disclosed in U.S. Pat. No. 2,814,200 (Hills), includes an air flow check device that prevents activation of a liquid flow meter by air flow. The float-activated valve is constructed to vent air that is entrapped in the system. In another system disclosed in U.S. Pat. No. 3,040,573 (Berck), the air to liquid ratio of the fluid being forced into the flow line is detected, and a signal is produced to operate valves to control the flow of fluid through the meter.
Therefore, an object of the invention is to provide liquid measurement system that overcomes the disadvantages of current metering systems to accurately and reliably measure the amount of waste grease or other liquid material that is passed through a metering device from a container to a receptacle or other location.